In the context of this specification, a “tethered ball” is a ball for use in tethered bat and ball games, having a tether cord attached at one end thereof to the impact body and to an anchor point at a location remote from the impact body and around which the impact body is struck.
Further in the context of this specification, a “streamer ball” is a ball for use in tennis or badminton type ball games, of a type having a tail comprising one or more elongate flexible streamers which are attached to the impact body for stabilizing the flight orientation of the impact body. Streamer balls of this type are known.
A streamer ball of this type is disclosed in U.S. Pat. No. 5,813,931 (assigned to Limpet Sports Management BV). The streamer ball comprises a ball and a tail comprising a number of elongate streamers directly attached to the ball and extending therefrom, for use in tennis-type bouncing ball games. U.S. Pat. No. 5,813,931 discloses a number of performance parameters for such a streamer ball and specifically for the tail of the ball, that provide for desired bounce and flight qualities that enable a tennis-type game to be played with such a streamer ball. The use of a tail connected to a ball has a number of benefits when playing a tennis-type ball game. Firstly, the use of a tail which trails behind the ball in flight creates drag which slows the ball down so that when the ball is struck with a bat, the distance that the ball can travel is effectively reduced, thereby permitting a tennis-type ball game to be played in a relatively small area while the ball can still be struck at “full strength”.
Yet a further benefit of such a tail is to reduce any tendency of the ball to spin or swerve during flight. The tail streams out behind the ball in flight so as to define a highly visible, dynamically changing and fluttering asymmetrical profile which rapidly reduces any side spin or top spin or swerve which is imparted to the ball upon impact by a bat, thereby causing the ball to follow a regular flight path.
Further benefits of such a tail include the reduction in flight speed provided by the tail which makes it easier to see the ball and a reduction in roll of the impact body on the ground which aids ball retrieval.
An important performance characteristic for a ball which is intended for use in tennis-type bat and ball games where the ball may be hit after it bounces, is that the ball should have sufficient bounce after striking a playing surface or being struck by a bat. A further important performance characteristic for a ball intended for use in tennis-type ball games, is that the ball should provide a solid feel and sound upon impact by a bat with minimal unpleasant handle vibration and a satisfactory rebound speed when leaving the bat after impact.
Strung racquets are usually provided with a network of strings under tension strung across a frame at the head of the racquet. When using a strung racquet, the resilient compressibility of the tensioned network of strings comprising the ball-striking surface of such a racquet, provides a “trampoline effect” which allows the ball to dwell on the ball-striking surface at impact for a significantly longer period of time than is the case with a bat which has an untensioned ball-striking surface. Due to the inherent resilient compressibility of the ball-striking surface of a strung racquet, the balls selected for use therewith can allow for less compression upon impact compared to a ball which is designed to be struck by a relatively rigid-faced bat. An important consideration in the design of a ball for use in bat and ball-type games played with a bat having an untensioned, rigid ball-striking surface, is that the ball should have sufficient resilient compressibility so that when it is struck by the bat, the dwell time of the ball upon the bat or playing surface at impact is sufficiently long as indicated by the relative depth of compression of the ball, so as to transfer adequate kinetic energy to the ball so as to provide the necessary spring off the bat or playing surface and consequently a satisfactory impact feel, sound and impact speed when leaving the bat after impact. The greater the compression of the ball upon impact, the greater the amount of energy which is stored in the ball which in turn causes greater spring off the bat when the energy is released as the ball regains its shape after the initial impact. There is thus a direct relationship between the depth of compression and the amount of energy which is stored by the ball upon impact and released immediately after full compression is achieved. It is for this reason that the current Applicant has sought to design a ball which has a high degree of resilient compressibility in order to achieve a high degree of spring off a bat.
A further important consideration in the design of balls for use in tennis-type bat and ball games played with bats having untensioned, rigid ball-striking surfaces, is that the balls should have sufficient mass in order for the ball to compress sufficiently upon impact in order to provide the trampoline effect referred to above, off a bat or playing surface and also to achieve solid contact between the ball and the ball-striking surface of a bat.
The Applicant has identified a need to supply bats having rigid, untensioned ball-striking surfaces having a relatively low weight. The cost of the bats in sets of bats and balls is the major component of such sets. It is an object of the present invention, to provide for the production of relatively lightweight bats which use less material and are thus relatively inexpensive to produce. It is also a requirement for bats which are to be used by children, that the bats must be relatively lightweight. In order to do so, it is necessary to provide balls for such bats which are correspondingly light in weight and which are matched in terms of their weight to the weight of the particular bat with which the balls are to be used. In this regard, the Applicant believes that such bats should be at least five times heavier than a ball to be used therewith and preferably, at least ten times heavier than the ball so as to provide a solid impact feel and avoid unpleasant jarring and vibration upon impact. It will therefore be appreciated that the balls used with such lighter bats must also be correspondingly light in weight. In tethered tennis-type games which have been around for many years the well known Swingball® tether tennis game uses a standard competition grade tennis ball which is tethered to a pole and which weighs between 56.0 g and 59.4 g without its anchor fitting. These sets are normally supplied with unstrung or untensioned rigid-faced plastic bats which weigh approximately 300 g, which weight has been found appropriate for rigid-faced, unstrung bats to use with these balls and which produce a solid, satisfactory, non-jarring impact feel. While this weight of bat works very well with a regulation tennis ball it has been found too heavy for younger children.
The Applicant has found that known commercially available lightweight balls are unsuitable for use with lightweight bats due to the low mass of such balls being unable to provide for the necessary compression of the ball upon impact with a bat in order to achieve the trampoline effect and a satisfactory solid contact between the ball and the ball-striking surface of the bat with minimal unpleasant handle vibration. The known lightweight balls tested by the Applicant are unable to achieve the compressibility and other requirements such as bounce height required for adequate impact performance, due to their lack of mass and other design characteristics.
It is an object of the present invention to provide a relatively lightweight flight controlled ball suitable for use in bat and ball games, wherein the impact body exhibits a sufficiently high degree of compression upon impact by a bat or playing surface so as to render the ball suitable for use with lightweight bats having untensioned, rigid ball-striking surfaces.